So when I tried this way I got the following output:
user'@'host:~$ doveadm -o plugin/mail_crypt_private_password=desired_password mailbox > cryptokey generate -u user -UR
user'@'host:~$
And when I tried this way I got the following output:
user'@'host:~$ doveadm -o plugin/mail_crypt_private_password=desired_password mailbox cryptokey generate -u user -UR
Folder Public ID
user'@'host:~$
In both cases I sent a new email to the server, and I got errors stating the mailbox can't be opened